Hello everyone! I need some help diagnosing my secondary air system. I just replaced the air pump and noticed that I have back pressure out of it after the system shuts off. I have vacuum going to the switch and going to the diverter valve during warm-up and when the air pump shuts down I still have vacuum going to the diverter valve. I also noticed that I have about 14.4 volts at the switch during the 30 second warm-up and when the air pump shuts down the voltage drops to 4.3 volts.

Why do I have voltage after the system shuts down? It seems like I should just replace the switch but I would like to be sure before I just throw money at it. I measured the ohms and it was about 44. When I disconnect the vacuum line going to the diverter valve it closes and I get no back pressure. Also, I have seen the richpin video, that's how I got this far

Back pressure refers to positive pressure. Vacuum is vacuum. Either a vacuum exists (supplied from the intake manifold only when the engine's running) or not. Blower pressure, when the blower is running, supplies air to the exhaust system when the combination valve opens, feeding air (from the electric air pump) into the exhaust manifold to help heat up the catalytic converter.

Maybe some info can help from the service manual.

The AIR system is used to reduce hydrocarbons (HC), carbon monoxide (CO) and oxides of nitrogen (NOX) exhaust emissions by heating up the catalytic converters quicker on cold engine start-up. The conversion of exhaust emissions to carbon dioxide (CO2) and water can occur sooner as the catalytic converter reach the normal operating temperature around 527°C (981°F). The AIR system consists of:

The air pump is a permanently lubricated turbine type pump which requires no periodic maintenance. The PCM runs the air pump for a certain length of time when the engine is started within a certain ECT range. When the air pump is commanded ON, the PCM will command an internal driver ON which pulls the air pump relay circuit to ground allowing current to flow to the air pump.

The air pump solenoid is used to control vacuum to the combination valve. When the air pump relay is commanded ON, air pump running), the PCM will wait a short amount of time to command the air pump solenoid ON. The PCM turns the solenoid ON by controlling an internal driver that pulls the solenoid circuit to ground. The PCM waits to turn the solenoid ON in order for the air pump to pressurize which keeps exhaust gas from entering the air pump.

When the air pump and air pump solenoid are turned ON, vacuum to the combination valve will allow the spring loaded diaphragm, upper valve in the combination valve, to be pulled up. This will allow pressurized air from the air pump to flow around the reed valve, lower valve in combination valve, to the exhaust manifold.

Before the PCM commands the air pump relay OFF, it will first command the air pump solenoid OFF and wait a short amount of time before it commands the relay OFF. This keeps exhaust gas from entering the air pump.

Thanks for the info fdryer. I'm getting exhaust into my air pump. That was the back pressure that I was referring to. The diverter valve is operating correctly. My solenoid may be the problem but I just wanted to make sure before I spent any money. Could it be stuck open and allow vacuum to pass through and keep the diverter valve open even after the computer tells it to turn off? When I measured the voltage at the connector it was 14.4V at start up, then it drops to 4.3V when the air pump shuts off. Is 4.3V enough to keep the solenoid open? When I shut the car off it drops to zero volts as it should. Do you know if I can measure the resistance to see if the solenoid is good. I did and got 44 ohms but I didn't have anything to reference that to

If you are seeing vacuum at the diverter valve after the air pump shuts off, then that solenoid switch is likely stuck open. Operating in this state will trash the new air pump, with hot exhaust flowing into it all the time.

That's what I was thinking, I definitely don't want to destroy my new air pump. My new solenoid should arrive tomorrow. I'll let you know if that's it. It's weird that it's stuck open instead of the other way but I guess it could happen. I wish I knew why the voltage remained after the system shuts down. Anybody else ever measure this and have the same results?

Electronic circuits can be confusing if not familiar with some quirks. Electronics sometimes forgoes using a relay to power solenoids. When this occurs, a power transistor is used. When an electronic circuit switches a power transistor off, residual voltage may be seen on the output side, where you're measuring at the solenoid connection. This is residual voltage with zero current behind it. With zero current at the wire, the solenoid isn't powered. Ignore it. Ask you need to know is if the solenoid powers up and if it opens or closes its own valve.

2001 SL-1, the air pump is no longer powering up. Do they go bad? Brushes? Can they be repaired? What should I check first, the Air Pump power relay???

Quote:

Originally Posted by fdryer

Back pressure refers to positive pressure. Vacuum is vacuum. Either a vacuum exists (supplied from the intake manifold only when the engine's running) or not. Blower pressure, when the blower is running, supplies air to the exhaust system when the combination valve opens, feeding air (from the electric air pump) into the exhaust manifold to help heat up the catalytic converter.

Maybe some info can help from the service manual.

The AIR system is used to reduce hydrocarbons (HC), carbon monoxide (CO) and oxides of nitrogen (NOX) exhaust emissions by heating up the catalytic converters quicker on cold engine start-up. The conversion of exhaust emissions to carbon dioxide (CO2) and water can occur sooner as the catalytic converter reach the normal operating temperature around 527°C (981°F). The AIR system consists of:

The air pump is a permanently lubricated turbine type pump which requires no periodic maintenance. The PCM runs the air pump for a certain length of time when the engine is started within a certain ECT range. When the air pump is commanded ON, the PCM will command an internal driver ON which pulls the air pump relay circuit to ground allowing current to flow to the air pump.

The air pump solenoid is used to control vacuum to the combination valve. When the air pump relay is commanded ON, air pump running), the PCM will wait a short amount of time to command the air pump solenoid ON. The PCM turns the solenoid ON by controlling an internal driver that pulls the solenoid circuit to ground. The PCM waits to turn the solenoid ON in order for the air pump to pressurize which keeps exhaust gas from entering the air pump.

When the air pump and air pump solenoid are turned ON, vacuum to the combination valve will allow the spring loaded diaphragm, upper valve in the combination valve, to be pulled up. This will allow pressurized air from the air pump to flow around the reed valve, lower valve in combination valve, to the exhaust manifold.

Before the PCM commands the air pump relay OFF, it will first command the air pump solenoid OFF and wait a short amount of time before it commands the relay OFF. This keeps exhaust gas from entering the air pump.

The air pump is just a blower motor using brushes no different from starters, blower motors and windshield wiper motors. They would eventually wear out; plain bearings, brushes and commutators. The best way to test the motor is direct wiring to the battery unless you're familiar with wiring circuits to use a jumper across the pump relay.

They definitely go bad on occasion, and if they don't run for a while, the downstream pipes will fill up with crud. This can cause a unit to not turn even if it was a bad relay or fuse if you ignore it for too long. It's only used for cold starts, but will throw a code if it doesn't work. If it doesn't work with direct power, make sure it turns freely and the pipes are clear. If it still doesn't work, it's time for a new or JY one.

The air pump is just a blower motor using brushes no different from starters, blower motors and windshield wiper motors. They would eventually wear out; plain bearings, brushes and commutators. The best way to test the motor is direct wiring to the battery unless you're familiar with wiring circuits to use a jumper across the pump relay.

Are the brushes replaceable, reachable or is this motor just like POS e-fan radiator fan motors that Croak every 3 years like clock work?

Although I'm not completely familiar with the air injection reaction system, the air pump runs for less than a few minutes on cold engine starts so the extra air pumped into the exhaust system helps the O2 sensor and/or the catcon heat up sooner. This tells me the blower should last beyond the average life cycle of the car. It isn't run anywhere near as long as the hvac blower motor left on all the time in some cars. The air pump motor isn't serviceable by GM standards, no different from GM never rebuilding starters or blower motors. Dealers replace with new oem parts. This doesn't stop starter rebuilds from creating a low cost replacement solution or with imported parts, brand new ones at far lower cost then oem and have proven to last several years witout issues.

The air pump isn't considered rebuildable unless an individual has some skills and familiarity with dc motors and can disassemble one to explore what's worn and deal with whether or not parts are available. Remember, the air pump isn't repaired, just replaced so if you decide on a tear down, you'd better consider where a source of parts are. This is outside the box thinking when attempting repairs on anything not considered repairable.

Tested the air blower, happy to say it works. I guess the power relay is next? Not sure what its called in the relay case? And possible fuse?

Quote:

Originally Posted by fdryer

The air pump is just a blower motor using brushes no different from starters, blower motors and windshield wiper motors. They would eventually wear out; plain bearings, brushes and commutators. The best way to test the motor is direct wiring to the battery unless you're familiar with wiring circuits to use a jumper across the pump relay.

Go back to post#2 and read it again. There's a specific sequence taking place with the blower powering up first(?) to pressurize before blowing fresh air into the exhaust manifold. The air pump relay in the fuse panel must be must be energized to close a set of contacts to send 12v power to the blower. You can test one side of this relay circuit by inserting a small wire jumper across the relay terminal sockets 30 and 87. This sends 12v power (fused) immediately to power the blower. If this side of the relay circuit powers the blower, the command side of the relay can be tested with a multimeter but only when starting up with a cold engine. Relay terminal sockets 85 and 86 are the command side, energizing the relay solenoid. Only one of these two terminals is electronically switched by the pcm driver, 12v or ground. Measuring both terminals for voltage should result in zero volts before starting then show 12v with a cold engine startup for about a minute or so. You may have to examine wiring between blower, ground and power from the relay.